1. Field of the Invention
The present invention relates to a vehicle driving information storage apparatus and a vehicle driving information storage method and in particular, to a data compression associated with an image storage and image processing as well as image compression ratio increase and image improvement in reproduction process.
2. Description of the Related Art
A vehicle driving information storage apparatus used for analysis of a traffic accident, a vehicle collision experiment, safety education, and the like should have at least a function for storing a state of a driver (or dummy) and a state in and out of the vehicle as images.
As shown in FIG. 8, a conventional vehicle driving information storage apparatus normally includes a first television camera 101 for filming a state out of the vehicle in the running direction of a vehicle 100 and a second television camera 102 for filming a state of the driver and a state inside the vehicle, so that images filmed by the television cameras 101 and 102 are respectively stored in video recorders 103 and 104 which function independently from each other.
Moreover, the image compression may be a reversible data compression in which an initial image can be completely reproduced after the image compression and a non-reversible data compression in which an initial image cannot be reproduced completely. From viewpoint of the data compression, the latter is more beneficial.
The data capacity can greatly be saved by sacrificing the color image gradation or using a gray scale image instead of a color image. However, the data capacity reduction in this way may not be appropriate depending on the object to be filmed. For example, when storing an image filmed by a security-associated monitor apparatus, in order to identify a person filmed, it is necessary to know the color of the clothes and the like. Moreover, in the case of a drive recorder or the like mounted on a vehicle and used for a driver education and an accident verification, it is necessary to detect from the filmed image at least a color of the traffic signal and the like.
In the aforementioned conditions, it is preferable to perform a full-color image filming which is continued for a comparatively long period of time especially in the case of monitor apparatus and the drive recorder. According, the amount of the stored image data becomes inevitably very large.
However, the first and the second television cameras 101 and 102 and the video recorders 103 and 104 should have a considerably high speed and accordingly, these apparatuses become elaborate and cost much. Moreover, each of the video recorders 104 and 104 operate independently from each other. When these video recorders are used for analysis of a traffic accident or a vehicle collision experiment, there is no guarantee of synchronization between these vide recorders even if they are rewound immediately after recovered. When they are not synchronized, it is difficult to correct the synchronization lag.
Furthermore, the first and the second television camera 101 and 102 and the video recorders 103 and 104 should always be set inside a vehicle when they are to be used for analysis of traffic accident or the like. Thus, a plurality of cameras and video recorders occupy a considerable space in the vehicle, disturbing the persons in the vehicle. Moreover, increase in weight may deteriorate the acceleration and brake functions of the vehicle.
Moreover, as the image data compression method for full color, the JPEG compression method including a sequential coding as a mode is widely used. However, when an image is stored with a high compression ratio, the image quality is deteriorated and it is impossible to obtain a sufficient resolution or sharpness. Currently, the compression ratio is lowered to obtain a high quality or the compression ratio is increased to save the data capacity. It is impossible to simultaneously obtain a high compression ratio and a high image quality.
Moreover, in the case of a monitor apparatus and a drive recorder, a fisheye lens is often used so as to film a wide range of area. Here the use of the fisheye lens is meaningless unless an image is formed on a film surface or a CCD light detecting surface without eclipse in the entire angle of the lens. On the other hand, the film surface and the CCD light detecting surface normally have a rectangular shape. In order to put a circular image formation into the rectangular shape, the diameter of the image should not exceed the length of the shorter side of the light detecting surface. That is, an unnecessary space is present at both sides of the light detecting surface and the image filmed is positioned at the center potion.
In the case of the data compression method of the sequential coding type, the image is scanned from left to right starting in the first line up to the last line from top- to the bottom so as to obtain an image data in a rectangular frame format. Accordingly, the shape of image that can be scanned is limited to a rectangular shape. Consequently, in order to scan a circular image, it is necessary to take at least an image of a rectangular shape circumscribed about the circle. Actually, the four corners of the rectangular shape are unnecessary space having no filmed image and input of an unnecessary data increases the image data capacity
It is therefore an object of the present invention to provide a vehicle driving information storage apparatus capable of storing a state inside and outside the vehicle and a state of the driver in synchronization, without disturbing the space inside the vehicle or causing a considerable weight increase, and that at a reasonable cost.
Another object of the present invention is to provide a vehicle driving information storage method having a high compression effect and capable of image compression and reproduction without deteriorating an image of a necessary portion.
The vehicle driving information storage apparatus according to the present invention is for storing image of a driver""s state and vehicle state and comprises: a wide angle lens arranged at a position capable of simultaneously filming a driver""s state and a state inside and outside a vehicle; a signal output unit for outputting as a digital signal each one shot of an image filmed by the wide angle lens; an image storage unit having a capacity to store a plurality of shots of digital signals output from the signal output unit and updating the digital signals output from the signal output unit at a predetermined cycle; a condition change detection unit for detecting a sudden change of a driving condition of the vehicle; and a necessary image data preserving unit inhibiting update of images after detection of a driving condition sudden change by the condition detection unit.
Among the images filmed by the wide angle lens at a predetermined cycle, the latest shots of image, for example, jmax shots of image are stored in the latest image storage unit. More specifically, the latest image storage unit has a capacity for storing jmax shots of image filmed by the wide angle lens. After the first jmax shots of image are stored, a new image is overwritten while erasing the oldest image, so that the latest jmax shots of image are always stored.
Upon detection of a driving condition sudden change by the condition change detection unit, a new image overwrite is performed a predetermined number of times which is smaller than jamx, for example, jmaxxe2x88x92x1 (0 less than x1 less than jmax) and then the necessary data preserving unit inhibits a new image overwrite in the latest image storage unit.
Accordingly, the latest image storage unit preserves images filmed x1 times at a predetermined cycle before the moment of the driving condition sudden change and images filmed jmaxxe2x88x92x1 times at a predetermined cycle after the moment of the driving condition sudden change.
Since the wide angle lens is used for simultaneously filming the driver""s state and the state inside and outside the vehicle, there is no need of setting a plurality of cameras and video recorders, which enables to reduce the apparatus size and the cost. The reduced size of the apparatus need not occupy a large space inside the vehicle, leaving a large free space. Moreover, since a single wide angle lens is used for simultaneously filming the driver""s state and the state inside and outside the vehicle, unlike the case using a plurality of cameras, there is no danger of synchronization lag between the images of inside and outside the vehicle.
Moreover, the apparatus comprises a first and a second latest image storage unit having different image update cycles arranged in parallel to each other.
The latest image storage unit having a shorter image update cycle, e.g., the first latest image storage unit contains images for accurate analysis of the driver""s state and condition changes inside and outside the vehicle immediately before and after a moment of occurrence of a driving condition sudden change. Moreover, the latest image storage unit having a longer image update cycle, e.g., the second latest image storage unit contains images for rough grasp of the driver""s state and condition changes inside and outside the vehicle for a comparatively long period of time before and after the occurrence of the driving condition sudden change.
In the latest image storage unit for storing images for a comparatively long period of time before and after an occurrence of a driving condition sudden change, the filming cycle is set long for image storage. Accordingly, even if an image is recorded over a long period of time, the storage capacity required for image storage is comparatively small.
Moreover, in the latest image storage unit for accurately storing the condition change before and after an occurrence of a driving condition sudden change, the filming cycle is set short for image storage. Accordingly, it is possible to accurately analyze a change caused instantaneously. In this latest image storage unit, an image is written at a short cycle but this unit is activated for only a limited period of time before and after the occurrence of the driving condition sudden change. Accordingly, there will not arise a problem of increasing the storage capacity.
Furthermore, a convex mirror is arranged within a field angle of the wide angle lens so that an image in a dead space of the wide angle lens is filmed via the convex mirror. Thus, it is possible to film various portions without increasing the number of filming lenses.
Moreover, the apparatus further comprises a condition detection unit for detecting a condition of a driver or a vehicle so as to be output as a digital data, which is stored in synchronization with the image update cycle. Thus, it is possible to store various data detected by the condition detection unit, together with an image without a synchronization lag.
When the condition detection unit is a acceleration sensor, it is possible to know a condition change before and after an acceleration sudden change due to a sudden brake or collision. This is helpful for analysis of a traffic accident, safety education, vehicle collision experiments, and the like.
Furthermore, when each of the latest image storage unit, the condition change detection unit, and the necessary image data preserving unit is provided with a power backup unit arranged independently of functional components of the vehicle, even if the vehicle is severely damaged by a collision, it is possible to obtain, store, and maintain an image data after the occurrence of the condition sudden change.
According to another aspect of the present invention, the image processing method for compressing an image using an irreversible compression algorithm in which an image quality is deteriorated as a compression ratio increases comprises steps of: dividing the image into a plurality of types of regions according to the image information importance in the image; setting different compression ratios for the types of regions in such a way that a region of a lower importance has a higher compression ratio than a region of a higher importance; generating a compressed data for each of the regions and storing the compressed data in a data storage medium together with a position information of the respective regions; and when reproducing the image, separately decompressing the compressed data of the respective regions stored in the data storage medium and relocating the data according to the position information of the corresponding region.
With this configuration, a low compression ratio is set for the region having a higher importance of image information and it is possible to prevent deterioration of the quality of the image of a higher importance. Moreover, for the region of a lower importance, a high compression ratio can be set independently of the compression ratio of the region of a higher importance. Accordingly, it is possible to significantly reduce the storage capacity of the entire compressed data. Images of the respective regions are compressed and reproduced independently from one another. The compressed data of the respective regions are stored in the data storage medium together with their position information and accordingly, at image reproduction, it is possible to correctly relocate a decompressed image so as to reproduce an original image.
It should be noted that a type of region may be dispersed at a plurality of region portions.
Moreover, the aforementioned object may be obtained by the method comprising steps of: dividing the image into a necessary region and an unnecessary region, so that the unnecessary region of the image is discarded and only the necessary region of the region is taken out to generate a compressed data which is stored together with a position information of the region in a data storage medium, and when reproducing the image, decompressing the compressed data of the necessary region stored in the data storage medium and relocating the decompressed data according to the position information.
With this configuration, the image data of the unnecessary portion will not be stored as a compressed data and it is possible to significantly save the compressed data capacity. Accordingly, even when an image compression of high image quality with a low compression ratio is performed, it is possible to reduce the capacity of the compressed data.
Furthermore, by applying simultaneously applying the aforementioned two configurations, it is possible to further increase the image compression efficiency. That is, the image processing method comprises steps of: dividing the image into a necessary region and an unnecessary region according to importance of the image information in the image and discarding the image of the unnecessary region; dividing the necessary region into a plurality of types of regions according to the importance of the image information in the necessary region; setting different compression ratios for the respective types of the regions in such a manner that a region of a lower importance has a high compression ratio than a region of a higher importance and generating a compressed data for each of the regions of the necessary region so as to be stored together with a position information of the respective regions in a data storage medium; and when reproducing the image, separately decompressing the compressed data of the respective regions of the necessary region and relocating the decompressed data according to the respective position information of the corresponding regions.
As has been described above, in the compression method of the sequential coding, the image which can be scanned is limited to a rectangular shape. When the aforementioned regions have irregular shapes, this compression method cannot be applied.
However, by dividing each of the regions into small rectangular areas, it is possible to apply the sequential coding to the respective regions for generating a compressed data. In this case, by storing the compressed data together with the position information of the small rectangular areas, it is possible to reproduce an original image.
A vehicle driving information storage apparatus according to the present invention comprises:
a compression condition setting block having: a region setting unit for setting a plurality of types of image storage regions for a memory taking in an image; and a compression ratio setting unit for setting a compression ratio of each of the image storage regions,
an image compression block having: a compression condition storage unit for storing the image storage regions set in the compression condition setting block, their position information, and compression ratios; a compressed data generation unit for generating a compressed data for each of the image storage regions according to the image storage regions and compression ratios stored in the compression condition storage unit; and a data storage medium for storing the compressed data generated by the compression data generating unit; and
an image reconstruction block having: a compressed data decompressing unit for separately decompressing the compressed data stored in the data storage medium according to the compression ratios stored in the compression condition storage unit for each of the image storage regions; and image reproduction an for relocating the decompressed data on an image reproduction memory according to the position information of the respective image storage regions stored in the compression condition storage unit and reproducing the image.
The region setting unit of the compression condition setting block is used for setting a plurality of types of image storage regions for the memory for taking in images and the compression ratio setting unit is used for setting a compression ratio for each of the image storage regions.
The image storage regions and their position information and compression ratios set in the compression condition setting block are stored in the compression condition storage unit of the image compression block. The compressed data generation unit of the image compression block generates a compressed data for each of the image storage regions according to the image storage regions and the compression ratio stored in the compression condition storage unit and stores the generated data in the data storage medium of the image compression block.
Moreover, the compressed data decompression unit of the image reconstruction block separately decompresses the compressed data of the respective image storage regions stored in the data storage medium according to the compression ratios stored in the compression condition storage unit and the image reproduction unit of the image reconstruction block relocates the decompressed data on memory for image reproduction so as to be reproduced according to the position information of the respective image storage regions stored in the compression condition storage unit.
With this configuration, it is possible to set an image storage region and its compression ratio according to an image to be handled. Accordingly, the apparatus can handle various images.
Moreover, among the components associated with the image processing apparatus, the compression condition setting block, i.e., the region setting unit and the compression ratio setting unit can be omitted by storing in advance image storage regions and their position information and compression ratios in the compression condition storage unit. Such a configuration is effective when the importance of the image information within an image is not changed, for example, when the image processing apparatus is constructed in a camera for a definite-point monitoring in which the same type of image is always located in the same position within an image.